Normal hearing individuals are capable of selectively paying attention to achieve speech intelligibility and to maintain situational awareness under noisy listening conditions such as restaurants, bars, concert venues etc. In contrast, it remains a daily challenging task for hearing impaired individual to listen to a particular, desired, sound source in noisy environments and at the same time to be environmentally aware. Already existing binaural hearing aid systems are very effective in improving the signal to noise ratio of a bilaterally or binaurally beamformed microphone signal relative to the originating microphone signal or signals supplied by the left ear and right ear microphone arrangements. The marked signal to noise ratio improvement of the bilaterally or binaurally beamformed microphone signal is caused by a high directivity index of the binaurally beamformed microphone signal which means that sound sources placed outside a relatively narrow angular range around the target direction, typically the user's frontal direction, are heavily attenuated or suppressed. The narrow angular range in which sound sources remain substantially unattenuated may extend merely +/−20-40 degrees around the target direction. This mechanism leads to an unpleasant so-called “tunnel hearing” sensation for the hearing impaired user which inter alia is characterized by a loss situational awareness.
U.S. Pat. No. 8,755,547 discloses a binaural beamforming method and binaural hearing aid system for enhancing the intelligibility of sounds. The method of enhancing intelligibility of sounds includes the steps of: detecting primary sounds emanating from a first direction and producing a primary signal; detecting secondary sounds emanating from the left and right of the first direction and producing secondary signals; delaying the primary signal with respect to the secondary signals; and presenting combinations of the signals to the left and right sides of the auditory system of a listener. U.S. Pat. No. 8,755,547 utilize the precedence effect for localization dominance only.
There is a need in the art for a binaural hearing aid systems which provide a flexible way to achieve speech intelligibility improvement by strong beamforming, i.e. applying a high directivity index, in a noisy listening environment and mitigate “tunnel hearing” “sensation in less adverse listening environments via a controllable level of off-axis acoustic signal sources placed outside the target direction or target range such as to the sides of and behind the user.